The Southern Proper Motion Program IV. The SPM4 Catalog

We present the fourth installment of the Yale/San Juan Southern Proper Motion Catalog, SPM4. The SPM4 contains absolute proper motions, celestial coordinates, and (B,V) photometry for over 103 million stars and galaxies between the south celestial pole and -20 deg declination. The catalog is roughly complete to V=17.5 and is based on photographic and CCD observations taken with the Yale Southern Observatory's double-astrograph at Cesco Observatory in El Leoncito, Argentina. The proper-motion precision, for well-measured stars, is estimated to be 2 to 3 mas/yr, depending on the type of second-epoch material. At the bright end, proper motions are on the International Celestial Reference System by way of Hipparcos Catalog stars, while the faint end is anchored to the inertial system using external galaxies. Systematic uncertainties in the absolute proper motions are on the order of 1 mas/yr.Comment: 34 pages, 8 figures, 3 tables; accepted for publication in AJ; note - modified author list and acknowledgements sectio

Characterization of a planar 8 mm wide radiofrequency atmospheric pressure plasma source by spectroscopy techniques

Atmospheric pressure planar radiofrequency (RF) 13.56 MHz discharge in Ar gas generated in a long gap is investigated. The discharge operation with and without a dielectric barrier on the electrodes is studied as a function of the applied power and gas flow. The source afterglow is characterized and is analyzed for possible large-scale biomedical applications where low gas temperature is required. The discharge is studied by relative and absolute emission spectroscopies. A gas temperature as low as 330 +/- 50 K is determined from the rotational-vibrational band of OH emission. The absolute value of the discharge continuum irradiation is used to determine the electron density and the electron temperature. The electron-atom and electron-ion contributions to the bremsstrahlung radiation are calculated and are compared with measured spectra. The electron density of 1.9 +/- 1 x 10(20) m(-3) and electron temperature of 1.75 +/- 0.25 eV are measured in the discharge without a dielectric barrier. It is found that presence of the dielectric has a negligible effect on electron temperature, whereas the electron number density is almost six times lower in the discharge with the dielectric barrier

The Southern Proper Motion Program III. A Near-Complete Catalog to V=17.5

We present the third installment of the Yale/San Juan Southern Proper Motion Catalog, SPM3. Absolute proper motions, positions, and photographic B,V photometry are given for roughly 10.7 million objects, primarily stars, down to a magnitude of V=17.5. The Catalog covers an irregular area of 3700 square degrees, between the declinations of -20 and -45 degrees, excluding the Galactic plane. The proper-motion precision, for well-measured stars, is estimated to be 4.0 mas/yr. Unlike previous releases of the SPM Catalog, the proper motions are on the International Celestial Reference System by way of Hipparcos Catalog stars, and have an estimated systematic uncertainty of 0.4 mas/yr. The SPM3 Catalog is available via electronic transfer,(http://www.astro.yale.edu/astrom/) As an example of the potential of the SPM3 proper motions, we examine the Galactocentric velocities of a group of metal-poor, main-sequence A stars. The majority of these exhibit thick-disk kinematics, lending support to their interpretation as thick-disk blue stragglers, as opposed to being an accreted component.Comment: 23 pages, 10 figures, accepted for publication in Astronomical Journa

Optical emission spectroscopy on Ar/N/sub 2/ and Ar/N/sub 2//C/sub 2/H/sub 2/ expanding thermal plasmas

This work has been carried out in connection with the possibilities to deposit carbon nitride materials by expansion thermal plasma assisted chemical vapour deposition (ETP-A-CVD). With the same technique high deposition rates and good quality a-Si:H and a-C:H materials have been obtained. A study of the intensity of atomic lines and molecular bands in a Ar/N/sub 2/ and Ar/N/sub 2//C/sub 2/H/sub 2/ expanding thermal plasma has been performed. In the case of the Ar/N/sub 2//C/sub 2/H/sub 2/ mixture rotational and vibrational temperatures were obtained by comparing computer simulated spectra of the CN(B/sup 2/ Sigma -X/sup 2/ Sigma , Delta v=0) spectral system bands with the experimental spectra. The CN ground state density is determined by taking into account the self-absorption of the CN band

Absolute Proper Motion of the Fornax Dwarf Spheroidal Galaxy from Photographic and HST WFPC2 Data

We have measured the absolute proper motion of the Fornax dwarf spheroidal galaxy from a combination of photographic plate material and HST WFPC2 data that provide a time baseline of up to 50 years. The extragalactic reference frame consists of 8 QSO images and 48 galaxies. The absolute proper motion is mu_alpha cos(delta) = 0.59 +-0.16 mas/yr and mu_delta = -0.15 +- 0.16 mas/yr. The corresponding orbit of Fornax is polar, with an eccentricity of 0.27, and a radial period of 4.5 Gyr. Fornax's current location is near pericenter. The direction of the motion of Fornax supports the notion that Fornax belongs to the Fornax-LeoI-LeoII-Sculptor-Sextans stream as hypothesized by Lynden-Bell (1976, 1982) and Majewski (1994). According to our orbit determination, Fornax crossed the Magellanic plane \~190 Myr ago, a time that coincides with the termination of the star-formation process in Fornax. We propose that ram-pressure stripping due to the passage of Fornax through a gaseous medium denser than the typical intragalactic medium left behind from the LMC may have caused the end of star formation in Fornax. The excess, anomalous clouds within the South Galactic pole region of the Magellanic Stream whose origin has long been debated in the literature as constituents of either the Magellanic Stream or of the extragalactic Sculptor group, are found to lie along the orbit of Fornax. We speculate that these clouds are stripped material from Fornax as the dwarf crossed the Magellanic Clouds' orbit.Comment: Accepted for publication in Astronomical Journal. The version with high resolution figures can be found at ftp://pegasus.astro.yale.edu/pub/dana/paper